Question

Water flows between two plates of which the upper one is stationary and the lower one is moving with a velocity V. What will be the velocity of the fluid in contact with the upper plate?

(a) V

(b) N ⁄ 2

(c) 2V

(d) 0

I had been asked this question in semester exam.

This interesting question is from Viscosity in section Properties of Fluids of Fluid Mechanics

Answer 1

The correct option is (d) 0

Best explanation: According to the No-Slip condition, the relative velocity between the plate and the fluid in contact with it must be zero. Thus, the velocity of the fluid in contact with the upper plate is 0 and that with the lower plate is V.